Ion guides with RF diaphragm stacks

• US 20060076485A1
• Filed: 10/04/2005
• Published: 04/13/2006
• Est. Priority Date: 10/05/2004
• Status: Active Grant

• Current Assignee: Bruker Daltonik GmbH (Bruker Corporation)
• Original Assignee: Bruker Daltonik GmbH (Bruker Corporation)
• Inventors: Franzen, Jochen, Stoermer, Carsten, Brekenfeld, Andreas, Wehkamp, Thomas
• Granted Patent: US 7,391,021 B2
• Time in Patent Office: Days
• US Class Current: 250/290
• CPC Class Codes: H01J 49/065 having stacked electrodes, e.g. ring stack, plate stack
• CPC Class Codes: H01J 49/42 Stability-of-path spectrometers, e.g. monopole, quadrupole, multipole, farvitrons

Abstract

The invention relates to RF voltage-operated ion guides based on stacked apertured diaphragms. The invention provides ion guides consisting of diaphragm stacks that permit the ion beam to be shaped in cross-section so that it corresponds to the acceptance profile of the subsequent section of the device, therefore yielding optimal ion transmission. For this purpose, at least some of the diaphragms in the diaphragm stacks do not have circular openings, but instead have openings which shape the cross section of the emerging ion beam in the desired manner. It is possible, for instance, to obtain elliptical beam cross sections, divided beams or beams focused to the shape of a fine thread at the output of the diaphragm stacks.

Claims

1. An ion guide consisting of one or more apertured diaphragm stacks comprising apertured diaphragms arranged with small intermediate spaces and insulated from each other, alternately supplied with the phases of an RF voltage, wherein at least some of the diaphragms have non-circular apertures.

2. An ion guide in accordance with claim 1, wherein some or all of the apertures have a longish, indented, peanut-formed, or more complex shape.

3. An ion guide in accordance with claim 1, wherein at least a part of the apertured diaphragms are rotated with respect to each other.

4. An ion guide in accordance with claim 1, wherein at least a part of the apertured diaphragms are similar to each other.

5. An ion guide in accordance with claim 1, wherein a potential profile is generated along the axis of one or more diaphragm stacks by means of electrical connections to the apertured diaphragms.

6. An ion guide in accordance with claim 5, wherein the potential profile along the axis changes with time.

7. An ion guide in accordance with claim 1, wherein the apertured diaphragms have narrow external protrusions;

wherein the mounts for the apertured diaphragms of the diaphragm stack are implemented in the form of electrical circuit boards into which the narrow protrusions of the apertured diaphragms are inserted; and

wherein the electrical circuit boards also contain the electrical components for supplying the RF voltage and, when used, the DC voltages.

8. An ion guide in accordance with claim 1, wherein the apertures in the diaphragms of at least one of the diaphragm stacks each have two hyperbolic indentations on opposite sides;

wherein the apertures of successive diaphragms are each turned through 900 with respect to the previous diaphragm; and

wherein the apertured diaphragms are alternately connected to the two phases of an RF voltage, as a result of which an RF quadrupole field is created within the apertured diaphragm stack.

9. An ion guide in accordance with claim 8, wherein DC voltages of opposing polarity are superimposed on the two phases of the RF voltage, with the effect that the quadrupole field only admits ions having a restricted range of specific masses.

10. An ion guide in accordance with claim 8, wherein DC voltages of opposing polarity are superimposed on the two phases of the RF voltage, and where the proportion of DC voltage changes from one apertured diaphragm to the next.

11. An ion guide in accordance with claim 10, wherein the two DC voltages of opposing polarity rise continuously from zero to a maximum value, thus creating a prefilter or postfilter for a precision mass filter.

12. An ion guide in accordance with claim 1, wherein the non-circular apertures in the region of the exit opening have an oblong shape and give rise to an output beam having an elliptical cross section.

13. An ion guide in accordance with claim 1, wherein the transition from a wide opening to an elongated one, then to one having the shape of a peanut shell with indentations and then to two separate openings generates a division of the ion beam into two partial beams.

14. An ion guide, wherein the first section of a diaphragm stack is implemented as an ion funnel, while a further section is arranged so that a quadrupole field is generated in its interior in accordance with claim 8.

15. An ion guide, wherein diaphragm stacks are combined, including diaphragm at least one stack in which a quadrupole field is generated in accordance with claim 8.

16. An ion guide in accordance with claim 15, wherein a precision mass filter is also incorporated.

17. An ion guide in accordance with claim 16, wherein the precision mass filter is preceded by a prefilter in accordance with claim 11.

18. An ion guide in accordance with claim 16, wherein the precision mass filter is operated at a pressure of between 0.01 and 1 Pascal.

19. An ion guide in accordance with claim 16, wherein a collision cell is incorporated, constructed as a diaphragm stack within which a quadrupole field is generated in accordance with claim 8.